"Adjust edit cage to modifier result " what does this do (with Mirror Modifier)?
WRT to Mirror modifier in 2.8 beta

In modelling I was using this feature with respect to the "MIRROR" modifier. Turning on "adjust edit cage to modifier result" basically Makes vertices and edges appear on the other side(instead of a plane surface) and also turns on the Selected part on the Mirroring side as well . Eg: If you select a vertex on the right side of the Symmetry, this feature will also highlight the Vertex on the Mirroring side.